The Republican National Committee has dropped Columbus, Ohio, and Phoenix, Arizona, from its list of potential 2016 convention cities, leaving just six contenders in the mix.

The committee announced Wednesday that Cincinnati, Cleveland, Dallas, Denver, Kansas City and Las Vegas have all advanced to the next round.

“In any other year, Columbus and Phoenix could have topped the list, but with so many strong cities competing, the committee had to make the difficult decision to narrow the field,” RNC site selection committee Chairwoman Enid Mickelsen said in a statement. “Phoenix and Columbus are great American cities, and I hope they’ll pursue a future bid for an RNC convention.”

Committee members will now schedule visits to each of the remaining cities to help determine the finalists. Those cities will then receive site visits from a full RNC delegation.

Hosting a convention can be a huge economic boon for a city, but it also requires having an adequate number of hotel rooms, solid security preparation and the ability to raise tens of millions of dollars to finance the event.